From the documentation:
MD_TCS230(uint8_t s2, uint8_t s3);
MD_TCS230(uint8_t s2, uint8_t s3, uint8_t oe);
MD_TCS230(uint8_t s2, uint8_t s3, uint8_t s0, uint8_t s1);
MD_TCS230(uint8_t s2, uint8_t s3, uint8_t s0, uint8_t s1, uint8_t oe);Various forms of the constructor for this class. The parameters are all the Arduino pin numbers used to control the nominated pins on the TCS230. The form used will depend on the configuration of the hardware connections to the Arduino. At a minimum S2 and S3 are required for color filter selection.
You can either use a constructor that includes the S0, S1 pins in the constructor, and the library will use them. If you don't specify them to the library then it is up to you to connected them to either GND or +5V. To see which makes sense in you situation, you need to look at the datasheet for the device and set accordingly.